Honeycomb structures (honeycomb filters) made of a ceramic are in use in order to capture the dust or another particulate matter contained in, for example, the exhaust gas emitted from automobiles (particularly, diesel engine automobiles) or the incineration gas generating during the incineration of waste, or to recover a product or a raw material from the high-temperature waste gas emitted in production processes of various industries. These honeycomb structures have a large number of through-holes surrounded by partition walls and extending in the axial direction of a honeycomb structure; the partition walls surrounding the through-holes have a filtration ability; a given number of the through-holes are plugged at one end of a honeycomb structure and the remaining through-holes are plugged at the other end of a honeycomb structure; thus, the honeycomb structures are formed so as to enable the capture and removal of the particulate matter contained in a dust-containing fluid. The ceramic-made honeycomb structures are superior in heat resistance and corrosion resistance and have suitable properties as a filter material used in a high temperature, corrosive gas atmosphere and, therefore, are in use for purification of various exhaust or waste gases.
A high-temperature exhaust or waste gas is often passed through such a honeycomb structure and, in that case, the honeycomb structure generates a thermal strain in various forms depending upon its thermal conductivity. Hence, in designing a honeycomb structure, it is necessary to grasp its thermal conductivity. However, since the honeycomb structure has a special construction, there has heretofore been established no method for measuring the thermal conductivity of the honeycomb structure per se without preparing a test specimen or the like.
As the method for measuring the thermal conductivity of a fine ceramic, there is, for example, a laser flash method which is specified in JIS R 1611. This method has restrictions; for example, the method is restricted to a material having a porosity of 10% or less and also to a test specimen of flat plate having, for example, a square shape of 10 mm×10 mm or less. Therefore, this method has been unable to apply to any honeycomb structure because of its material and shape. Further, the method has had an operational problem because a test specimen need be prepared.
The present invention has been made in view of the above-mentioned problems and aims at providing a method for measurement of thermal conductivity of a honeycomb structure which can measure the thermal conductivity of a honeycomb structure in the shape of the honeycomb structure per se or in a predetermined block shape without preparing, for example, a test specimen of particular shape.